1. Technical Field
The present invention generally relates to integrated circuit design and layout, and in particular to reference voltage distribution devices and methods.
2. Description of the Related Art
Certain circuit functions common to, for example, high speed serial links and other performance-based integrated systems require accurate voltage references. Typically, a voltage reference provides precision voltages for linear regulators, bias circuits, signal detection circuits, transmitters, and many other circuit functions. Technology limitations for providing quality silicon, as well as the industry trends in reducing reference voltages, create challenges for distributing precision voltage references to cores on a multiple-core integrated circuit (IC). Hence, for example, the ability to use a simple bandgap voltage reference with sufficient accuracy for each core is becoming increasingly more difficult. While trimmable bandgap technologies are well known, implementation of such technology in multiple-core ICs is impractical due to the resources required for the trimming process. Expending such resources for a multiple-core IC is unacceptable unless it is implemented only once per IC and at a central location.
Accurately distributing a precision voltage reference from a central location on an IC to multiple cores is a difficult task. Voltage offsets in the IC's ground grid between two points can reduce the accuracy of the voltage reference when the voltage reference is distributed in a single-ended fashion. Distributing an accurate differential reference on an IC has been investigated; however, the known technology often requires at each core location a differential receiver with multiple amplifier stages to maintain high input impedance. The multiple input offsets of the amplifiers can again reduce the accuracy of the distributed voltage reference.